Technical Field
This disclosure relates generally to techniques for optimizing the efficiency with which a pyrolysis tube of a material deposition apparatus operates and, more specifically, to methods for optimizing the efficiency with which a pyrolysis tube cracks a precursor material, such as a parylene dimer.
Related Art
Various material deposition processes require that a precursor material be pyrolyzed into activated species. The activated species then react with one another to form a polymer. Polymerization may occur on the surface of a substrate and, thus, the polymer is said to be deposited onto the substrate.
These general processes are used to deposit parylene (unsubstituted or substituted poly (p-xylylene)) films. Typically, the precursor material used for a parylene film is a [2.2]paracyclophane dimer. Pyrolysis of the dimer, and the subsequent deposition of a parylene thin film is a complicated dynamical process that includes the following steps:
During pyrolysis, the two strained C—C bonds of the dimer shown in FIG. 1a are cleaved to yield two di-radicals, or “monomers.” This reaction typically occurs inside a pyrolyzer at a temperature of about 600° C. In FIG. 1b, the activated monomer molecules that were created within the pyrolyzer are introduced into a deposition chamber, and condense onto a surface of a substrate within the deposition chamber. The monomers polymerize on the surface to produce a polymer coating.